Administrator Guide

NOTE: Dell Networking recommends that only experienced network administrators change the Rapid Spanning Tree
group parameters. Poorly planned modification of the RSTP parameters can negatively affect network performance.
The following table displays the default values for RSTP.
Table 85. RSTP Default Values
RSTP Parameter Default Value
Forward Delay 15 seconds
Hello Time 2 seconds
Max Age 20 seconds
Port Cost:
• 10-Gigabit Ethernet interfaces
• Port Channel with 10-Gigabit Ethernet interfaces
Port Cost:
• 2000
• 1800
Port Priority 128
To change these parameters, use the following commands.
• Change the forward-delay parameter.
PROTOCOL SPANNING TREE RSTP mode
forward-delay seconds
The range is from 4 to 30.
The default is 15 seconds.
• Change the hello-time parameter.
PROTOCOL SPANNING TREE RSTP mode
hello-time seconds
NOTE:
With large configurations (especially those configurations with more ports) Dell Networking recommends
increasing the hello-time.
The range is from 1 to 10.
The default is 2 seconds.
• Change the max-age parameter.
PROTOCOL SPANNING TREE RSTP mode
max-age seconds
The range is from 6 to 40.
The default is 20 seconds.
To view the current values for global parameters, use the show spanning-tree rstp command from EXEC privilege mode.
Enabling SNMP Traps for Root Elections and Topology
Changes
To enable SNMP traps, use the following command.
• Enable SNMP traps for RSTP, MSTP, and PVST+ collectively.
snmp-server enable traps xstp
Modifying Interface Parameters
On interfaces in Layer 2 mode, you can set the port cost and port priority values.
• Port cost — a value that is based on the interface type. The previous table lists the default values. The greater the port cost, the less
likely the port is selected to be a forwarding port.
• Port priority — influences the likelihood that a port is selected to be a forwarding port in case that several ports have the same port
cost.
To change the port cost or priority of an interface, use the following commands.
Rapid Spanning Tree Protocol (RSTP)
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